How about Stepmania Based champ?

how about a DDR based champ who would rely on swift reflexes to master.

something like in between every auto attack a prompt to press Q or W would pop up and you get like 2 seconds to press it but the length of the prompt scales with attack speed and so with more AS the window to press it get shorter and shorter down to like .5 seconds.

but for each prompt pressed correctly adds to a 1 stack to a combo(think the point counter from Osu). and the higher your combo the higher your DPS. and maximum combo stacks (30?) you go into a RAVE for a couple seconds and gain massively enhanced mobility and combat stats.

for an Ult it could be like Nhe Zha's ultimate from Smite where you have to quickly press whatever randomized QWE prompts AND correctly time clicks to maximize damage

Character design wise the could could be a teenage Techno Ninja who sorta looks like a DJ. and for his homeguard animation he uses Inline skates and leaves behind a neon afterimage.

so to summarize: first of all much similar to DJ Sona the character gets to Enjoy ambient music that changes depending on his combo stacks

Passive: for each correctly pressed prompt you gain Tempo stack. At max tempo stacks you gain 45% movement speed and 100% armor pen for 5-7 seconds. some of Your abilities are disabled by default however After every auto attack a prompt will appear to press the key and use the corrosponding ability.

Q: when activated your next attack will slow your target by 20/30/40/50% While in Rave mode this effect is automatically activated W: when activated your next attack will give you 20/30/40/50% movespeed during Rave mode this effect is automatically activated E:Throw a fan of daggers. the number of Daggers and damage is amplified by your Tempo stacks. If your In Rave mode the cooldown of this move is drastically lowered. R:Stun and snare a target champ while you dealing damage to them.during this ultimate a barrage of Prompts will appear for each one correctly pressed you will deal extra damage. if EVERY PROMPT is correctly pressed then you will automatically fill your tempo and enter Rave mode.